Phosphorus acid functionalized coating composition

ABSTRACT

The present invention relates to a composition comprising an aqueous dispersion of submicron-sized polymer particles and micron-sized polymer beads, wherein the polymer particles or beads or both are functionalized with phosphorus acid groups. The composition of the present invention is useful for providing a matte finish on substrates, such as leather, textiles, wallboard, decorative coatings, concrete, and wood, with improved stain resistance. The present invention also relates to a leather substrate coated with a clear matte finish comprising an acrylic or styrene-acrylic polymer film and micron-sized polymer beads, wherein the film or the beads or both are functionalized with a phosphorus acid monomer.

BACKGROUND OF THE INVENTION

The present invention relates to a phosphorus acid functionalizedcoating composition comprising a stable aqueous dispersion of polymerparticles (a latex) and micron-sized polymeric beads.

Leather upholstered automotive seats and furniture coated with lighttoned pigments tend to readily display stains created by users of thearticle. Stains transfer from an occupant's clothing to the upholsteredarticle at the point of the contact between the clothing and thearticle. The contact point between the occupant's clothing and theleather article is a clear topcoat that is applied to the leather as athin film, typically between 5 μm to 30 μm in thickness, and is a firstline of defense for protection of the upholstered article againststains. It is most desirable that the topcoat resist the transfer ofstain to avoid the need for abrasive cleaning, which tends todeteriorate the topcoat. Accordingly, it would desirable in the field ofcoatings for a variety of substrates including leather, textiles, andwood to find a topcoat composition that makes cleaning of thesesubstrates easier.

SUMMARY OF THE INVENTION

The present invention addresses a need in the art by providing, in oneaspect, a composition comprising an aqueous dispersion of 1) polymerparticles having an average particle size of from 50 to 300 nm; and b)polymer beads having an average particle size of from 2 to 30 μm;wherein the polymer particles or the polymer beads or both comprise from0.1 to 5 weight percent structural units of a phosphorus acid monomer.

In a second aspect, the present invention is an article comprising aleather substrate coated with clear matte finish comprising an acrylicor styrene-acrylic polymer film and polymer beads having an averageparticle size of from 2 to 30 μm; wherein the acrylic or styrene-acrylicpolymer film or the polymer beads or both comprise from 0.1 to 5 weightpercent structural units of a phosphorus acid monomer. The compositionof the present invention is useful for providing a matte finish onsubstrates, such as leather, textiles, wallboard, decorative coatings,concrete, and wood, with improved stain resistance.

DETAILED DESCRIPTION OF THE INVENTION

The present invention addresses a need in the art by providing, in oneaspect, a composition comprising an aqueous dispersion of 1) polymerparticles having an average particle size of from 50 to 300 nm; and b)polymer beads having an average particle size of from 2 to 30 μm;wherein the polymer particles or the polymer beads or both comprise from0.1 to 5 weight percent structural units of a phosphorus acid monomer.

The term “structural unit” is used herein to describe the remnant of therecited monomer after polymerization. For example, a structural unit ofmethyl methacrylate is as illustrated:

-   -   structural unit of methyl methacrylate        where the dotted lines represent the points of attachment of the        structural unit to the polymer backbone.

Similarly, a structural unit of phosphoethyl methacrylate is asillustrated:

-   -   Structural unit of phosphoethyl methacrylate        where R is H or

The composition of the present invention is advantageously prepared bycombining separately synthesized aqueous dispersions of polymer beadsand polymer particles. The aqueous dispersion of beads can be preparedby a variety of methods such as those disclosed in US Pat. Pub.2013/0052454; U.S. Pat. Nos. 4,403,003; 7,768,602; and 7,829,626. Theaqueous dispersion of beads is preferably prepared by multistep thermalpolymerization using a gradual addition process.

In the first step of a preferred process, a surfactant, a suspensionstabilizing agent, and water are combined with a) an oil solubleinitiator; b) first monomers comprising one or more firstmonoethylenically unsaturated acrylate monomers that form a film-forminghomopolymer at room temperature (that is, a low T_(g) monomer); and c)optionally a multiethylenically unsaturated monomer. The surfactant ispreferably an anionic surfactant such as the sodium salt of a C₁₀-C₁₄alkylbenzene sulfonate. Examples of suitable suspension stabilizingagents include hydroxyethyl cellulose (HEC), polyvinyl pyrrolidone(PVP), and gelatin; examples of suitable oil soluble initiators includelauroyl peroxide (LPO) and benzoyl peroxide (BPO); examples of suitablefirst monoethylenically unsaturated acrylate low T_(g) monomer ormonomers include butyl acrylate, ethyl acrylate, and 2-ethylhexylacrylate, and combinations thereof. Preferably, a multiethylenicallyunsaturated monomer such as allyl methacrylate, trimethyolpropanetriacrylate, trimethyolpropane trimethacrylate, or divinyl benzene isalso copolymerized in this first step.

More preferably, surfactant, HEC at a concentration of preferably from0.2, more preferably from 0.5 weight percent, to preferably 5, morepreferably to 3 weight percent based on the weight of total monomer, andwater are combined in the first step with a) lauroyl peroxide or benzoylperoxide; b) butyl acrylate or 2-ethylhexyl acrylate or a combinationthereof; and c) allyl methacrylate, wherein the weight-to-weight ratioof butyl acrylate or 2-ethylhexyl acrylate or a combination thereof toallyl methacrylate is in the range of from 99:1, more preferably from98:2, to preferably 92:8, more preferably to 94:6.

The first monomer or monomers are emulsified and polished, thenthermally polymerized by gradual addition as follows: A mixture ofwater, surfactant, rheology modifier, and the polished emulsion are fedto a reactor and heated and maintained at 75° C. to 90° C. for asufficient time to polymerize the first monomer or monomers; thereafter,one or more second monomers comprising one or more secondmonoethylenically unsaturated acrylate or styrenic monomers are added,either neat or in the form of an emulsion. The second monoethylenicallyunsaturated monomer or monomers preferably comprise a monomer which,when polymerized, is not film forming at room temperature (that is, ahigh T_(g) monomer). Examples of suitable preferred secondmonoethylenically unsaturated monomers include styrene and methylmethacrylate. Preferably, the second monomers comprise a) styrene ormethyl methacrylate or a combination thereof; and b) a phosphorus acidmonomer, preferably phosphoethyl methacrylate. Most preferably, thesecond monomers comprise methyl methacrylate and phosphoethylmethacrylate at a weight-to-weight ratio 99.5:0.5, and more preferablyfrom 99:1, to 92:8, more preferably to 94:6, and most preferably from96:4.

The ratio of the first monomer or monomers to the second monomer ormonomers is preferably in the range of from 1:1, and more preferablyfrom 2:1, to 10:1, more preferably to 8:1, and most preferably to 6:1.The polymer beads preferably have a hard domain, characterized by aT_(g) greater than 40° C., as calculated by the Fox equation, and a softdomain, characterized by a T_(g) of less than 25° C., as calculated bythe Fox equation. Preferably the weight-to-weight ratio of the soft tothe hard domains is from 1:1, and more preferably from 2:1, to 10:1, andmore preferably to 8:1. More preferably, the hard domain isfunctionalized with phosphorus acid groups.

The resultant polymer beads have an average particle size of from 2, andmore preferably from 5 μm, to 30, more preferably to 20, and mostpreferably to 15 μm as measured by a Malvern Mastersizer 2000 Analyzerequipped with a 2000 uP module.

The stable aqueous dispersion of polymer particles (the latex) used inthe composition of the present invention is preferably an acrylic or astyrene-acrylic latex, which can be conveniently prepared by emulsionpolymerization. The latex can be prepared in a single stage or multiplestages and is preferably prepared in a 2-stage process. In an example ofa preferred 2-stage process, a phosphorus acid monomer, preferablyphosphoethyl methacrylate, is emulsion polymerized in a first stage witha low T_(g) monomer, preferably ethyl acrylate, butyl acrylate, or2-ethylhexyl acrylate, and, optionally, a carboxylic acid monomer suchas acrylic acid or methacrylic acid under conditions sufficient to formthe aqueous dispersion of first stage polymer particles.

Preferably, the concentration of the phosphorus acid monomer in thisfirst stage is preferably from 0.1, and more preferably from 0.2 weightpercent, to preferably 5, and more preferably to 3 weight percent basedon the weight of first stage monomers. A carboxylic acid monomer ispreferably used at a concentration of from 0.1, and more preferably from0.2 weight percent, to preferably 8, more preferably 5 weight percent,based on the weight of first stage monomers. The low T_(g) monomer,preferably butyl acrylate or 2-ethylhexyl acrylate, is preferablypresent at a concentration of from 30, and more preferably from 40weight percent, to preferably 99.9, more preferably to 99, and mostpreferably to 97 weight percent, based on the weight of total firststage monomers.

In an example of a preferred second stage, a high T_(g) monomer,preferably methyl methacrylate, styrene, or butyl methacrylate, morepreferably methyl methacrylate or styrene, is combined with the stableaqueous dispersion of first stage polymer particles under emulsionpolymerization to form the 2-stage aqueous dispersion of polymerparticles. The dispersion of polymer particles is preferablyfilm-forming at less than or equal to 25° C., more preferably less thanor equal to 20° C. and preferably greater than or equal to −60° C., andmore preferably greater than or equal to −30° C.

In another example of a preferred 2-stage process for preparing theaqueous dispersion of polymer particles, a high T_(g) monomer isemulsion polymerized in a first stage with a low T_(g) monomer andoptionally low levels (˜0.1 to 1 weight percent) of a carboxylic acidmonomer and a multiethylenically unsaturated monomer to form an aqueousdispersion of a first stage monomer. The concentration of the low T_(g)monomer is preferably from 40 to 50 weight percent, and theconcentration of the high T_(g) monomer is from 50 to 60 weight percent,based on the weight of monomers in the first stage.

In a second stage, similar concentrations of high and low T_(g) monomersas used in the first stage are emulsion polymerized, preferably in thepresence of a phosphorus acid monomer, preferably phosphoethylmethacrylate to form the 2-stage aqueous dispersion of the polymerparticles. The concentration of the phosphorus acid monomer in thisembodiment is preferably in the range of from 0.1, more preferably from0.3 weight percent to 5, more preferably to 3 weight percent, based onthe weight of monomers in the second stage.

The average particle size of the polymer particles is from 50, and morepreferably from 80 nm, to 300, and more preferably to 250 nm as measuredusing a Brookhaven B190 particle analyzer.

It is critical that either the polymer beads or the polymer particlesare functionalized with phosphorus acid groups, and it is preferred thatboth the polymer beads and the polymer particles are functionalized withphosphorus acid groups. The polymer particles preferably arefunctionalized with from 0.1, and more preferably from 0.2 weightpercent, more preferably from 0.3 weight percent, to preferably 5, morepreferably to 4, and most preferably to 3 weight percent structuralunits of a phosphorus acid monomer, based on the weight of the polymerparticles. Similarly, the beads are preferably functionalized withpreferably from 0.1, more preferably from 0.2, more preferably from 0.3,and most preferably from 1 weight percent, to preferably 5, and morepreferably to 3 weight percent structural units of a phosphorus acidmonomer, based on the weight of the polymer beads.

The weight-to-weight ratio of polymer beads to polymer particles ispreferably from 10:90, more preferably from 30:70, and most preferablyfrom 40:60 to preferably 80:20, more preferably 70:30, and mostpreferably to 60:40.

The aqueous dispersions of polymer beads and polymer particles arecombined to form the composition of present invention. The compositionmay further include one or more ancillary materials including rheologymodifiers, flow agents, coalescents, feel modifiers, defoamers,crosslinking agents, and surfactants. Although pigments may also beincluded, it is preferred that the composition contains a substantialabsence of pigments, that is, less than 4, preferably less than 1, morepreferably less than 0.1, and most preferably 0 weight percent ofpigments, based on the weight of the composition.

The composition of the present invention is useful as a matte coating,preferably a clear matte coating, for a variety of substrates includingleather, textiles, metal, concrete, and wood. It has been surprisinglydiscovered that coated substrates prepared from the compositions of thepresent invention, particularly coated leather substrates, exhibitimproved stain resistance as compared with coatings prepared fromcompositions comprising polymer particles and polymer beads that are notfunctionalized with phosphorus acid groups.

In another aspect, the present invention is an article comprising aleather substrate coated with clear matte finish comprising a) anacrylic or styrene-acrylic polymer film; and b) polymer beads having anaverage particle size of from 2 to 30 μm; wherein the acrylic orstyrene-acrylic polymer film or the polymer beads or both, comprise from0.1, preferably from 0.2 weight percent to 5, preferably to 3 weightpercent structural units of a phosphorus acid monomer. More preferably,the polymer beads and the polymer film are both functionalized withstructural units of a phosphorus acid monomer. Preferably the particlesize of the polymer bead is from 5 μm, to preferably 20, and morepreferably to 15 μm as measured by a Malvern Mastersizer 2000 Analyzerequipped with a 2000 uP module.

Abbreviations Chemical Name HEC CELLOSIZE ™ QP-3L Hydroxyethyl CellulosePEM Phosphoethyl methacrylate (60% active) ALMA Allyl methacrylate 2-EHA2-Ethylhexyl acrylate MMA Methyl methacrylate MAA Methacrylic acid AAEMAcetoacetoxy ethyl methacrylate BA Butyl Acrylate AA Acrylic AcidA-16-22 Polystep A-16-22 Surfactant B5N Polystep B5N Surfactant LauroylPeroxide Luperox LP organic initiator t-BHP t-Butyl hydroperoxide (70%in water) APS Ammonium persulfate IAA Iso ascorbic acid FF6M BruggoliteFF6M Reducing Agent SSF Sodium formaldehyde sulfoxylate EC-3085A4-Hydroxytempo antioxidant (5% in water) 1.5LX KATHON ™ 1.5LX BiocideRM-825 ACRYSOL ™ RM-825 Rheology Modifier RM-8W ACRYSOL ™ RM-8W RheologyModifier RM-2020 ACRYSOL ™ RM-2020 Rheology Modifier 2229W ROSILK ™2229W Feel Modifier Abbreviations Chemical Name (cont'd) Fluid HAquaderm Fluid H flow agent Laponite Laponite RD (2.7% in deonizedwater) Texanol Texanol coalescent BYK-022 BYK-022 defoamer CF-10TRITON ™ CF-10 surfactant

(CELLOSIZE, KATHON, ROSILK, ACRYSOL, and TRITON are all Trademarks ofThe Dow Chemical Company or its Affiliates);

Method for Measuring Particle Size Distribution in Polymer Beads

Particle size distributions of beads were determined using lightdiffraction a Malvern Mastersizer 2000 Analyzer equipped with a 2000 uPmodule. Approximately 0.5 g of bead dispersion samples were pre-dilutedinto 5 mL of 0.2 weight percent active Triton 405 in degassed, DI water(diluents). The pre-diluted sample was added drop-wise to the diluentfilled 2000 uP module while the module was pumped at 1100 rpm. Red lightobscurations were targeted to be between 4 and 8%. Samples were analyzedusing a Mie scattering model (particle real refractive index of 1.48 andabsorption of zero: Diluent real refractive index of 1.330 withabsorption of zero). A general purpose (spherical) analysis model with“normal sensitivity” was used to analyze the diffraction patterns andconvert them into particle size distributions.

Intermediate Example 1—Preparation of Large Particle Sized BeadContaining 4% PEM Preparation of the Monomer Emulsion:

A mixture of A-16-22 (4.24 g), HEC (13.2 g), and DI water (800 g) wascombined with stirring with a mixture of ALMA (21.3 g), 2-EHA (511.25g), and lauroyl peroxide (3.04 g) in a 5-L vessel and emulsified using aPolytron PT10-35 rotor-stator homogenizer with a PCU-11 controller. Theresultant emulsion was polished for 1 min with the controller's power atsetting 2, thermally polymerized under gradual-addition conditions.

Thermal polymerization using a gradual addition process:

A mixture of DI water (350 g) and EC-3085A (0.11 g) was added to areactor and the contents heated to 80° C. The stage 1 polished emulsionwas fed to the reactor over 1 h. Upon completion of the feed, thereactor was held at 80° C. for about 30 min, after which time a stage 2emulsion consisting of MMA (127.4 g) and PEM (5.3 g, 60% active) wasthen fed into the reactor over 45 min. The reaction temperature was heldat 80° C. for 15 min then cooled to 65° C., whereupon a solution offerrous sulfate (7 g, 0.15% aqueous) and VERSENE EDTA (1.0 g, 1.0%aqueous) were added to the reactor. t-BHP (4 g) dissolved in water (20mL) and IAA (2 g) dissolved in water (20 mL) were fed separately intothe reactor over 30 min, after which time the reactor was allowed tocool to room temperature. The resulting emulsion was then filteredthrough a 100-mesh screen. Particle Size was measured at 8.8 μm; percentsolids was 33.4% with a gel number of 170 ppm.

Intermediate Example 2—Preparation of Large Particle Sized BeadContaining 2% PEM

This intermediate was prepared substantially as described forIntermediate Example 1 except that the ratio of MMA to PEM was 98:2 andthe w/w ratio of Stage 1 to Stage 2 was 80.4/19.6. Particle Size wasmeasured at 16.4 μm; percent solids was 34.6% with a gel number of 182ppm. Differences in particle sizes observed were believed to be due todifferences in homogenization power input and time.

Intermediate Examples 3 and 4—Preparation of Large Particle Sized Beadwithout any Phosphorus Acid Functionalization

These intermediates were prepared using substantially the same proceduredescribed for the preparation of Intermediate Example 1 except fordifferences in the monomer profile, as reflected in Table 1. In eachinstance, the beads were not functionalized with phosphorus acid groups.In Table 1, Stg 1 and Stg 2 refer to the compositions of the first andsecond stages of the beads, respectively. In each case, the ratio ofStage 1 to Stage 2 beads was ˜80:20.

TABLE 1 Bead Compositions and Particle Sizes Int. Ex. # 1 2 3 4 Stg 1 96EHA/4ALMA 96 EHA/4 ALMA 96 BA/4ALMA 98 EHA/2ALMA Stg 2 97.6 MMA/2.4 PEM98 MMA/1.2 PEM 96 MMA/4 EA 100 MMA PS (μm) 8.8 16.4 4.5 9.4

Intermediate Example 5—Preparation of PEM-Containing Latex

Monomer Emulsion 1 (ME1) was prepared by mixing water (200.9 g), B5N(23.3 g), A-16-22 (23.3 g), BA (598.45 g), AA (21.75 g), and PEM (3.9g); Monomer Emulsion 2 (ME2) was prepared by mixing water (10 g) and MMA(155.03 g).

Water (757.5 g) was added to a four-neck 5-L round bottom flask equippedwith a mechanical paddle stirrer, a thermocouple, N₂ inlet, and refluxcondenser. The water was purged with N₂ and heated to 35° C., whereuponME1 (213.54 g) was added with stirring. After 1 min, aqueous solutionsof iron sulfate heptahydrate (0.01 g in 2.5 g water), APS (0.16 g in 15g water), and sodium dithionite (0.31 g in 15 g water) were addedsequentially to the flask and the mixture was allowed to exotherm to 55°C. and maintained at 55° C. for 5 min. The mixture was cooled to 48° C.,whereupon EC-3085A (2.55 g), the remainder of ME1, aqueous solutions ofAPS (0.46 g in 15 g water), and sodium dithionite (0.78 g in 15 g water)were added sequentially to the flask. The contents of the flask wereallowed to exotherm to 74° C. and maintained at 74° C. for 10 min, atwhich time aqueous solutions of t-BHP (0.35 g in 5 g water) and SSF(0.28 g in 15 g water) were added sequentially to the flask. After a5-min hold, the mixture was cooled to 64° C., at which time ME2, aqueoussolutions of t-BHP (0.71 g in 7.5 g water), and FF6M (0.54 g in 15 gwater) were added sequentially to the flask. The contents of the flaskwere allowed to exotherm to 74° C. and controlled at 74° C. for 15 min,after which time aqueous solutions of t-BHP (1.17 g in 17.5 g water) andFF6M (1.02 g in 20 g water) were added sequentially at rates of 0.62g/min respectively 0.7 g/min with concomitant cooling to 30° C. B5N(55.42 g) and an aqueous solution of triethylamine (14.35 g in 125 gwater) were added to the cooled flask at a rate of 4.27 g/min followedby addition of an aqueous solution of hydrogen peroxide (0.63 g in 5 gwater), then an aqueous solution of 1.5LX (2 g in 2.5 g water) at a rateof 0.45 g/min. After completion of the feeds, the contents of the flaskwere filtered to remove any gel. The filtered dispersion was found tohave a solids content of 34.7%, negligible gel, and a pH of 7.2.

Intermediate Examples 6, 7 and 8 were prepared substantially by the sameprocedure as described for Intermediate Example 3, except differences inmonomer profile as reflected in Table 2.

In Table 2, Stg 1 Comp and Stg 2 Comp refer to the compositions of themonomers used in the first and second stages to prepare the latexes. Stg1:Stg 2 refers to the ratio (w/w) of Stage 1 to Stage 2 monomers.

TABLE 2 Latex compositions Int. Ex. # 5 6 7 8 Stg 1 Comp 96 BA/0.3 PEM/94.5 BA/1.2 PEM/ 45 BA/54.1 MMA/ 96.5 BA/3.5 AA 3.5 AA 3.5 AA 0.4MAA/0.5 ALMA Stg 2 Comp 100 MMA 100 MMA 45 BA/43.5 MMA/3 PEM/ 100 MMA 1MAA/7.5 AAEM Stg 1:Stg 2 80/20 80/20 40/60 80/20

Formulation preparation: Using a 0.25-L plastic container and a 3-bladepitched metal stirrer, the materials listed in Table 3 were added in theorder listed and mixed for at least 5 min after all materials wereadded. Int. Ex. refers to intermediate example, C1 refers to comparativeexample 1, and C2 refers to comparative example 2. All numbers in Table3 represent weights in grams.

TABLE 3 Pigment free topcoat formulations Example No. 1 2 3 4 C1 C2 Int.Ex. 6 84.7 84.7 Int. Ex. 7 103.92 103.92 Int. Ex. 8 84.7 84.7 RM-8250.48 0.48 0.48 0.48 Fluid H 3.14 3.14 3.14 3.14 2229w 3.76 3.76 3.763.76 RM-825 0.48 0.48 0.48 0.48 Int. Ex. 1 41.3 Int. Ex. 2 38.8 57.0Int. Ex. 3 41.98 Int. Ex. 4 57.0 39.5 Laponite 22.2 22.2 22.2 22.2dilution water 39 37.1 26.72 26.72 39 36.3 RM-825 7.5 7.3 6.7 7 Texanol3.15 3.15 Byk-022 0.62 0.62 CF-10 0.53 0.53 RM-8W 3.22 3.22 RM-2020 4.844.84 Total (g) 200.0 200.0 200.0 200.0 200.0 200.0

Stain Testing Procedure:

Topcoats were cast onto a white vinyl Leneta chart with a 7-mil Dowlatex applicator and dried for 7 d in a CTR (72° F. (˜22° C.), 50%R.H.). After 7 d, a number of ½-inch (1.2-cm) sections were markedacross the test panels equal to the number of stains to be tested. Thestains were placed in the test areas for 1 h. The tested stains includedtea, grape juice, coffee, and red wine. After 1 h, excess stains wereremoved using Kimwipes wipers and the test panel was placed on aAbrasion Tester (washability machine). A household sponge was loadedwith 10 mL of non-abrasive scrub media (Leneta) and 15 mL of water. Thesponge was placed in a 1-lb (0.45 Kg) abrasion boat and 200 cycles werecompleted using the abrasion tester. After cycles were completed thetest panels were rinsed, allowed to dry and then rated based on thepercent stain removal: (1=10% through 10=100% stain removal).

Table 4 illustrates the Results of Hydrophilic Stain Resistant Tests forthe Examples and Comparative Examples

TABLE 4 Hydrophilic Stain Resistance Results Ex. No. 1 2 3 4 C1 C2 PEMin latex? Yes Yes Yes Yes No No PEM in Bead? Yes Yes Yes No No No Stainresults Tea 7 7 8 6 2 2 Coffee 9 9 9 7 5 5 Redwine 6 6 7 5 2 2Grapejuice 7 7 7 5 4 4 Rating of 1-10 in which 10 represents completestain removal.

The results demonstrate a dramatic improvement in stain resistance forthe compositions that contain latex binder and bead both functionalizedwith PEM (Examples 1-3) and even a measurable improvement across theboard for a composition that contains PEM in the latex binder only(Example 4) as compared with compositions that contain no phosphorusacid functionalization in either the latex binder or the beads(Comparative Examples 1 and 2).

1. A composition comprising an aqueous dispersion of polymer beadshaving an average particle size in the range of from 2 to 30 μm, whereinthe beads comprise a hard domain having a T_(g) greater than 40° C. anda soft domain having a T_(g) less than 25° C.; wherein the beadscomprise from 0.1 to 5 weight percent structural units of a phosphorusacid monomer.
 2. The composition of claim 1 wherein the soft domain ofthe polymer beads comprises structural units of a multiethylenicallyunsaturated monomer.
 3. The composition of claim 2 wherein theweight-to-weight ratio of the soft domain to the hard domain is in therange of from 1:1 to 10:1.
 4. The composition of claim 3 wherein thehard domain of the polymer beads is functionalized with from 0.1 to 5weight percent of the phosphorus acid monomer.
 5. The composition ofclaim 3 which further comprises polymer particles having an averageparticle size in the range of from 50 nm to 300 nm, wherein the polymerparticles are film-forming at less than or equal to 25° C. and greaterthan or equal to −60° C.
 6. The composition of claim 5 wherein theweight-to-weight ratio of polymer beads to polymer particles is from30:70 to 70:30.
 7. The composition of claim 1 which further comprises asuspension stabilizing agent which is hydroxyethyl cellulose, polyvinylpyrrolidone, or gelatin.
 8. The composition of claim 2 wherein the harddomain is functionalized with structural units of a) the phosphorus acidmonomer; and b) methyl methacrylate or styrene or a combination thereofat b:a ratio in the range of from 99.5:0.5 to 94:6.
 9. The compositionof claim 8 wherein the soft domain of the polymer beads comprisesstructural units of butyl acrylate or 2-ethylhexyl acrylate or acombination thereof.
 10. The composition of claim 9 wherein themultiethylenically unsaturated monomer is allyl methacrylate,trimethyolpropane triacrylate, trimethyolpropane trimethacrylate, ordivinyl benzene.
 11. The composition of claim 1 wherein the phosphorusacid monomer is phosphoethyl methacrylate.